CHAPTER X - Hilton's Law

    In the years l860-61-62 a series of lectures was delivered by John Hilton, F. R. S., F. R. C. S., "On the Influence of Mechanical and Physiological Rest in the Treatment of Accidents and Surgical Diseases, and the Diagnostic Value of Pain." These lectures were afterward published in book form under the title of "Rest and 'Pain." This book is a medical classic and worthy of careful perusal by all students of medicine.

    The careful observations and reasonings therefrom which are reported in "Rest and Pain" explain many of the phenomena noted in osteopathic practice.  We desire to give all due honor to this man who was so far in advance of his time.

    We will quote a few paragraphs from "Rest and Pain" which have a direct bearing on osteopathic methods of diagnosis and therapeutics.

    The Law Stated. - After careful study of the distribution of nerves throughout the body, Hilton sums up his observations in a terse sentence which we choose to call a law - "The same trunks of nerves whose branches supply the groups of muscles moving a joint, furnish also a distribution of nerves to the skin over the insertion of the same muscles, and the interior of the joint receives its nerves from the same source."

    Hilton further states that "Every fascia of the body has a muscle attached to it, and that every fascia throughout the body must be considered as a muscle."

    Methods of Studying Anatomy. - These statements lead us to a closer study of each joint and its controlling muscles and governing nerve or nerves.  We may study anatomy under artificial divisions such as Osteology, Syndesmology, Myology, etc., and still, after securing an accurate technical knowledge of details, we have nothing of practical value.  It is in the correlation of these tissues with their interdependence quite fully understood that we have a working knowledge.  With this thought of the influence of one tissue on another and the harmonious action secured by the comparatively varied distribution of the nerve trunks, we find a new and vital interest in anatomy.

    This law is based upon the facts of anatomy and physiology, and makes our concrete knowledge of these subjects of constant practical value in both diagnosis and therapeutic. This law shows us the "why" of certain vital and mechanical manifestations, and teaches us practical methods of treatment.

    Example of Hilton's Law. - An example of Hilton's law is the distribution of the sciatic nerve to the ankle.  The muscles moving the joint, the synovial membrane and most of the skin over the joint are all innervated by it.

    The Knee. - The knee has three nerves.  Each one has a motor and sensory control.  The extensor muscles and the skin over them is innervated by the anterior crural.  The flexor muscles and the skin over them is innervated by the sciatic.  The obturator, in addition to these nerves, furnishes sensory filaments to the synovial membrane.  All the joints of the body may be examined in the light of this law.  The same segment of the central nervous system which gives off a purely motor nerve trunk, gives off also a sensory nerve whose filaments are distributed over the same area.  Thus it is sometimes necessary to go to the central nervous system to discover this association of motor and sensory distribution.  In practice we always do this, because it is easier to work from the center of the areas of distribution.

    The Object of Such a Distribution. - Hilton says: "The object of such a distribution of nerves to the muscular and articular structures of the joints, in accurate association, is to insure mechanical and physiological consent between the external muscular, or moving force, and the vital endurance of the parts moved, namely, of the joints, thus securing in health a true balance of force and friction until deterioration occurs."

    "Without this nervous association in the muscular and articular structures, there could be no intimation by the internal parts of their exhausted condition." "Again, through the medium of the muscular and cutaneous nervous association great security is given to the joint itself by those muscles being made aware of the point of contact of any extraneous force or violence.  Their involuntary contraction instinctively makes the surrounding structures tense and rigid, and thus brings about an improved defence for the subjacent structures."

    The Uniformity of the Law. - "This articular, muscular and cutaneous distribution of the nerves is, in my opinion, a uniform arrangement in every joint in the body.  We may find numerous illustrations of the same method of distribution in other parts of the body, which have the same definite relations to each other, and in this respect present the same physiological and mechanical arrangement observable in joints. This same principle of arrangement, anatomically, physiologically and pathologically considered, is to be observed with an equal degree of accuracy in the serous and in the mucous membrane. Thus considered, it presents a principle which, if it has any application in practice, must be one certainly of large extent."

    Precision of Nervous Distribution to Muscles. - "The great precision with which muscles are supplied by their nerves is worthy of remark; and is such that if we have before us a contracted muscle, we may be sure of the nerve which must be the medium, or the direct cause of it."

    "In studying the supply of nerves to muscles over every part of the body, we find a great degree of precision, which marks one difference between their distribution and that of the arteries."

    Indications for Use of Therapeutics. - I should say in aid of other means, employ this cutaneous distribution of nerves as a road or means toward relieving pain and irritation in the joint.  You thus quiet the muscles, prevent extreme friction, and reduce muscular pressure and spasm.  Therapeutics may certainly reach the interior of this joint and its muscles through the medium of the nerves upon the surface of the skin, and so induce physiological rest to all the parts concerned in moving the joint.

    The advantage to be derived arises in this way: Sensibility of the filaments supplying the skin being reduced, that influence is propagated through the sensitive nerves to the interior of the joint and to the muscles moving a joint.  This diminution of sensibility tends to give quietude or perfect rest to the interior of the joint, which is one of the most important elements towards the successful issue of the treatment of cases of this kind."

    The Use of Hilton's Law in Physical Diagnosis. - Hilton's law is applicable in physical diagnosis.  The osteopath makes constant use of the superficial expressions of nerve activity.  After having learned the whole course, distribution and central connections of the nerve, we can judge rightly as to the structures involved by noting the physiological conditions of all the structures innervated by a definite nerve trunk.  Hilton applied his law entirely from the physiological side, i. e., he observed changes in the relations of joint structures, but considered the deformity as due to excessive physiological action of the muscles in their effort to secure rest for the joint surfaces.  This is largely true, but he did not question how the process was initiated.  The osteopath seeks a point of stimulus to the nerves controlling a joint or other structure, believing that it is of little value to anaesthetize nerve endings and give. rest so long as this stimulus is allowed to arouse impulses in the nerve fibers.

    Comparison of Methods. - To compare methods of using Hilton's Law, we will note one of his cases, and a similar one treated osteopathically.  In Chapter VIII of "Rest and Pain" he describes a case of inflammation of the shoulder joint, and mentions that the joint is fixed in a position of rest as a result of the association of nerves to the synovial membrane, the muscles of the joint and the skin over the joint.  Anaesthesia releases the fixedness of the joint, because the muscles do not contract after the sensory impulses are deadened by the anaesthetic.  He says, "Therapeutics may certainly reach the interior of this joint and its muscles through the medium of the nerves upon the surface of the skin, and so induce physiological rest to all parts concerned in moving the joint.  I mean to say that these nerves upon the surface of the skin being in direct association with the interior of the joint itself, we may reduce the muscular spasm as well as the sensibility of the interior portion of the joint, by applying our anaesthetics with accuracy and with sufficient intensity upon the exterior of the deltoid muscle, over the distribution of these sensitive filaments.  The thought will occur to you at once that there is nothing very remarkable in this opinion, and that is quite true.  The embrocations, however, which would ordinarily be suggested for this purpose, are not of a character sufficiently potent to alleviate the pain of the patient, and are, I believe, seldom employed with a definite idea in the mind of the prescriber.  I would suggest that we should employ our fomentations strongly. medicated with belladonna, with opium or with hemlock, instead of using mere fomentation of hot water.  Some will say, 'Oh, hot water is quite as good;' but I can assure you practically that it is not so."

    You will note that he makes use of the cutaneous reflexes to affect the interior of the joint.

    A recent case, corresponding we believe, was treated osteopathically with marked success.  The inflammation in the shoulder joint was not traumatic in origin nor did it appear to be rheumatic in character.  Hot fomentations would give great relief, but did not give sufficient rest to the joint to permit of a cure.  The fear was entertained that longer rest of the articulation would result in adhesion and loss of function in the joint.  Since the circumflex nerve appeared to be the one involved, a careful examination was made of the articulation . s between the sixth and seventh cervical vertebrae.  The circumflex nerve is made up largely of fibers from the sixth cervical nerve trunk.  Tension and tenderness, together with slight rotation of the sixth cervical were noted at this point.  The osteopath, instead of working over the area of distribution of the circumflex, centered his work upon this articulation to bring about right relations between the sixth and seventh cervical vertebrae.  Tension and irritation were removed.  The circumflex nerve ceased to manifest any undue irritation.  The osteopath almost invariably works from the center to periphery instead of the reverse.

    Herpes Zoster. - An example of the osteopath's use, or rather recognition of Hilton's law: A case of Herpes Zoster located along the course of the left fifth intercostal nerve was given a grave prognosis by a homeopathic physician.  The patient visited an osteopath immediately, hoping that some relief might be found for the intolerable pain.  The eruption extended from the spine to the median line in front, forming a band about one inch wide.  The fifth rib was found rotated downward, thus lessening the fifth intercostal space and pressing on the nerve at some point in its course.  This rib was raised, even though the osteopath's fingers rested directly upon the eruption, in order to force the rib upward.  The result was most gratifying.  Pain decreased almost immediately, and there was a rapid change in the appearance of the eruption, the firey red giving place to a paler color.  Those papules which were just forming subsided, and those which had formed vesicles began immediately to scab.

    The patient could not stand erect, lifting the arm caused increase of pain, likewise inspiration was lessened because it caused pain.  Hilton would say that these movements were curtailed to give physiological rest.  From the osteopathic standpoint, they are reflexes which are not reparative in character, hence must be eliminated.  Every movement which tended to separate the fifth and sixth ribs caused pain, hence the patient refrained from making them.  The osteopath separated these ribs, even though the process of doing so caused pain.  The structural defect causing the irritation was removed.  In view of the fact that Herpes Zoster is associated with posterior ganglionitis, it may be that the subluxation of a rib is a secondary lesion and hence only a secondary cause of pain.  Clinical experience teaches us that relief is obtained in these cases by separating the ribs which are approximated by the muscular tension.

    The Distribution of an Intercostal Nerve. - The distribution of an intercostal nerve is to the pleura, intercostal muscles and skin over these muscles, thus corresponding to the distribution of nerve trunks to the synovial membrane of a joint, the muscles moving the joint and the skin covering the joint.

    Some of the Evil Results of Rest. - If we give rest to all structures in which pain is located, we will help to fill the world with stiff joints and serous adhesions, to say nothing of the far reaching after affects of these structural defects upon the functional activity of the nervous system.  A differential diagnosis is required in all cases of painful joints in order to determine whether it is wise to disturb the physiologically protective reaction.

    Hilton's law may be called an anatomical law; there do not appear to be any exceptions to it, especially when supplemented by his statement that "every fascia of the body has a muscle attached to it, and every fascia throughout the body must be considered as the insertion of a muscle." This carries the influence of motor nerves to points covered by their sensory companions.

    Head's Law. - Another law, or in this case a comprehensive statement, has been made by Head in his writings in "Brain." This is a statement of physiological transference of pain from its point of origin to a point of conscious sensation.  This physiological law is stated as follows: "When a painful stimulus is applied to a part of low sensibility in close central connection with a part of much higher sensibility, the pain produced is felt in the part of higher sensibility rather than in the part of lower sensibility to which the stimulus was applied."

    Application of the Law. - This physiological law can be applied in two ways.  First, we may consider the relative sensibility of different portions of a nerve trunk.  If a stimulus is applied to a nerve trunk at some point in its course between its origin and distribution, the pain caused by the stimulus will be felt, in the area of distribution of the fibers of this nerve trunk rather than at the point where the stimulus is applied.  The skin, mucous or serous membrane and muscle in which sensory nerves end are areas of high sensibility compared with the trunk of the nerve.  The brain is conscious of only the areas of distribution of the sensory nerves, hence stimuli applied at the points of low sensibility are referred to the areas of high sensibility.  Thus all lesions causing pressure upon nerve trunks cause pain, contraction, or perversion of secretion in the areas of distribution.  The patient is not thoroughly conscious of any location but the area of distribution which is an area of high sensibility.

    The cases described under Hilton's law are applicable here.  In the case of inflamed shoulder joint the patient was not conscious of the irritation at the spinal column the rotated vertebra - this was an area of low sensibility in the course of the nerve trunk.  The brain attributed all the trouble to the terminations of the nerves in the tissues of the joint.  All of the reflexes acted accordingly.

    The second application of this law is to the relative intensity of areas of high sensibility.  The areas in which sensory nerves end are all areas of high sensibility, but some are higher than others.  We note in practice that sometimes a nerve trunk which supplies several structures will manifest pain in a portion of its area of distribution which is not the part in which the irritation is located.  For example, the sensory portion of the obturator nerve is distributed to the hip joint and skin on the inner side of the knee.  The skin seems to be an area of higher sensibility than the interior of the hip joint, because in disease of the hip joint the patient frequently complains of pain in the cutaneous area rather than in the joint where the actual disease is located.

    The Viscera. - The viscera are normally nonsensitive, i. e., we are not conscious of possessing viscera, The pressure of food in the stomach and the beat of the heart make no impression on our consciousness; and so it is with all parts of the body governed by sympathetic nerves.  The viscera are areas of low sensibility, not low irritability, for they are richly supplied with sensory nerves, upon the stimulation of which active functioning depends.  The response to stimuli of sensory nerves in viscera is rapid, but normally this response takes place entirely outside of our consciousness, the impression is not recognized as corning from the viscera, but from a remote area of high sensibility in close central connection with the less sensitive area.  As an example, pain is felt in the right shoulder, as a result of hyperaemia of the liver.  The pressure upon sensory nerves in the liver does not cause pain in the liver, but refers it to a more sensitive area - the skin and muscles of the right shoulder.

    Chronic inflammation of the stomach may cause no consciousness of pain in that organ, but may cause intense aching in the mid-dorsal region.

    Nerves of Conscious Sensation. - Cerebrospinal nerves are nerves of consciousness, and seem to have the duty of registering on the sensorium of our brains not only their own impressions, but the impressions derived from that part of the sympathetic system in closest central connection with them.

    A close study of the segmental distribution of spinal nerves and their connection with the sympathetic system by the rami-communicantes will make Head's law of practical value in osteopathic diagnosis and therapeutics.